1. Field of the Invention
The present invention relates to a magnetic head which performs magnetic recording or reproduction of information to or from a magnetic recording medium by slidably contacting the magnetic recording medium with a magnetic core and more particularly to a magnetic head having a magnetic core which is sandwiched by sliders that slidably contact the magnetic recording medium together with the magnetic core.
2. Description of the Prior Art
As a magnetic head of the above-described type, there is a magnetic head which is used in a floppy disc drive or "FDD" that performs magnetic recording or reproduction of information to or from a disc-shaped magnetic recording medium such as a flexible magnetic disc, i.e., a floppy disc. The conventional magnetic head for a floppy disc drive will be explained with reference to FIGS. 1-4.
FIG. 1 shows an arrangement of a body of a magnetic head. In FIG. 1, reference numeral 1 denotes a core assembly. The core assembly 1 is arranged as a combination of a recording/reproduction core 2, a magnetic core for recording and reproduction, and an erasing core 4, as a magnetic core for performing so-called tunnel erasure, i.e., for erasing a magnetic recording at both ends of a recording track, with their respective front core portions being connected to each other via a spacer 6.
The recording/reproduction core 2 includes a T-shaped first front core 2a, an I-shaped second front core 2b being connected with the first front core 2a via a recording/reproduction gap 3, and a rear core 15 as a third core being connected with rear ends of the first and second front cores 2a and 2b to magnetically connect the rear end of the first front core 2a with that of the second front core 2b.
The erasing core 4 includes a T-shaped first front core 4a, an I-shaped second front core 4b being connected with the first front core 4a via erasing gaps 5a and 5b, in the same manner as the above-described recording/reproduction core 2, and a rear core 16 as a third core being connected with rear ends of the front cores 4a and 4b.
However, the recording/reproduction core 2 and the erasing core 4 are connected to each other via the spacer 6 to form the core assembly 1 before they are connected to their rear cores 15 and 16, respectively. Non-magnetic sliders 7 and 8 are connected on both sides of the assembly core 1 by means of adhesion bond or glass welding or the like thereby to sandwich the core assembly 1 therebetween.
The sliders 7 and 8, together with the recording/reproduction core 2 and the erasing core 4, contact slidably a magnetic disc (not shown) to stabilize the slidable contact of the both cores 2 and 4 on the magnetic disc and reinforce the cores 2 and 4. The sliders 7 and 8 are made of ceramic materials or the like. The sliders 7 and 8 have notches 7a and 8a, respectively and are formed as blocks each having a L-shaped cross section. The sliders 7 and 8 each have a side face opposing the core assembly 1. The side faces have respective projected faces projecting toward the core assembly 1, the projected faces being located at upper portions above the notches 7a and 8a as shown in FIG. 1, respectively. The projected faces of the sliders 7 and 8 as bonding faces 7b and 8b are connected to both side faces of upper end portion of the core assembly 1 by means of adhesion bond or glass welding.
After the connection, a coil bobbin 9 on which a coil 10 for recording or reproduction is wound around, and a coil bobbin 12 on which a coil 13 for erasing is wound around, are fitted to the core assembly 1 so that the front cores 2a and 4a are inserted into respective cavities of the coil bobbins 9 and 12. Consequently, the rear cores 15 and 16 connected to each other via a spacer 17 are connected to the rear ends of the front cores 2a, 2b, 4a and 4b to arrange a magnetic head body 18 as shown in FIG. 2.
As shown in FIG. 1, the above-described coil bobbins 9 and 12 include respective rectangular-shaped bodies having holes 9a and 12a, and flanges 9b and 12b being formed at both ends of the bodies to restrict the winding widths of the coils 10 and 13, respectively.
FIG. 2 is a perspective view of a side of the whole magnetic head opposing a magnetic disc, and FIG. 3 is a perspective view showing the rear side of the whole magnetic head shown in FIG. 2. In FIGS. 2 and 3, reference numeral 19 designates a magnetic head. The magnetic head 19 is assembled by positioning at a predetermined position of a support plate 20 made of stainless steel or phosphor bronze and fixing a magnetic body 18 on the position, by connecting the support plate 20 to a flexible printed board 21 for conducting it to an external circuit, and by connecting coil ends 10a and 13a to the flexible printed board 21.
As shown in FIG. 4, a squared cylindrical-shaped shield ring 22 surrounding the magnetic head body 18 is mounted on the magnetic head 19.
The magnetic head 19 is mounted on a floppy disc drive (not shown) by fixing the support plate 20 to a head carriage in the floppy disc drive. The magnetic head 19 performs magnetic recording or reproduction of information to or from the magnetic disc by slidably contacting the magnetic disc which is rotating, with an upper face shown in FIG. 2 of the magnetic head body 18 serving as a sliding face.
The above-described shield ring 22 is made of a shielding material for shielding the magnetic head body 18 from external noise, such as noise due to leakage flux from a permanent magnet in a disc drive motor used in the floppy disc drive, and high frequency noise generated from a display close to the floppy disc drive when the floppy disc drive is assembled in a system. The shield ring 22 is made of a high magnetic permeability material, such as Permalloy, or a high conductivity material, such as aluminum or copper, or combination of these materials.
Reduction in size of disc drive units has been recently promoted, various noise sources have been arranged close to the magnetic head 19 and accordingly the shield ring 22 has become an indispensable element.
In the conventional magnetic head for the floppy disc drive, the coil ends 10a and 13a, respectively, are connected to connection parts 21a of the printed board 21 by soldering. However, upon connecting, it is troublesome to carry out positioning of the coil ends 10a and 13a to the connection portions 21a properly and it takes a considerably long time to perform the soldering. In addition, when heated for a long time, the connection portions 21a are peeled off from the printed board, which makes the soldering step a very difficult step to perform. The soldering step has been an obstacle to simplification of steps for manufacturing magnetic heads.
In a composite type magnetic head which will be explained later on, there are many coil ends and accordingly the above-described problems are more severe. In addition, a lack of ample space for arranging components is a serious problem hindering the composite type magnetic head from commercialization. In order to solve these problems, a bobbin terminal type magnetic head has been proposed in which the coil bobbins 9 and 12 are provided with terminal portions.
FIGS. 5-7 show the conventional bobbin terminal type magnetic head. In FIGS. 5-7, those parts or components corresponding to those in FIGS. 1-3 are designated by the same reference numerals and detailed explanations thereof are thus omitted.
FIG. 5 shows a magnetic head body of the bobbin terminal type magnetic head. As shown in FIG. 5, coil bobbins 9 and 12 to be fitted to the front cores 2a and 4a, respectively, of the core assembly 1, have terminal holding portions 9c and 12c formed at one end of flanges 9b and 12b, respectively. A plurality of terminals 9d and 12d made of an electroconductive material are planted on the bobbin terminal holding portions 9c and 12c, respectively.
A coil for recording/reproduction 10 and an erasing coil 13 are wound around the coil bobbins 9 and 12, respectively, and then coil terminals 10a and 13a of the coils 10 and 13, respectively, are wound around terminals 9d and 12d, respectively, a plurality of times according to their arrangement and soldered.
On the other hand, the sliders 7 and 8 are formed with notches 7c and 8c, respectively, which serve as escape spaces for the bobbin terminal holding portions 9c and 12c, respectively, and with reinforcing portions 7d and 8d, respectively, for increasing bonding area between the core assembly 1 and the sliders 7 and 8 to increase the connection strength therebetween and thus connection strength between the support plate 20 and the sliders 7 and 8. These components are assembled in the same manner as shown in FIGS. 1 to 3 to arrange the magnetic head body 18.
FIG. 6 is a rear face perspective view showing the magnetic head body shown in FIG. 5 in a state where the magnetic head body is mounted onto a support plate. As shown in FIG. 6, the magnetic head body 18 is fixed to the support plate 20 after properly positioning thereon. The support plate 20 is formed with first escape spaces 20a for rear cores 15 and 16 which continue to second escape holes 20b for terminals 9d and 12d. The terminals 9d and 12d of the coil bobbins 9 and 12, respectively, are projected so as to pass through the second escape holes 20b to arrange on a rear face of the support plate 20, i.e., on a face opposite to a face where the slidable contacting face of the magnetic head body is disposed.
FIG. 7 is a perspective view showing the rear face of the magnetic head shown in FIG. 6 in a state where a printed board is mounted on the support plate 20. As shown in FIG. 7, a plurality of connection portions 21a are arranged on a printed board 21 at positions corresponding to the terminals 9d and 12d. The connection portions 21a are formed with holes 2lb through which the terminals 9d and 12d are inserted. The terminals 9d and 12d and the connection portions 21a are connected by, for example, soldering to arrange the magnetic head 19.
In the bobbin terminal type magnetic head thus arranged, it is easy to connect between the coil ends 10a and 13a and the connection portions 21a. However, the terminal holding portions 9c and 12c provided on one end of the flange 9b and on one end of the flange 12b, respectively, of the coil bobbins 9 and 12 tend to be deformed due to heat applied thereto at the time of connecting the coil ends 10a and 13a to the terminals 9d and 12d by soldering.
Attempts to prevent thermal deformation of the terminal holding portions 9c and 12c by increasing their size has been unsuccessful because there is a restriction on space. If it were possible to increase the size of the terminal holding portions 9c and 12c, it would also be necessary to increase the size of the notches 7c and 8c provided in the sliders 7 and 8, respectively, which serve as escape spaces for the terminal holding portions 9c and 12c. If this were done, the connection strength between the sliders 7 and 8 and the support plate 20 would decrease. Furthermore, in that case, it would also be necessary to increase the size of the escape holes 20b in the support plate 20 for passing the terminals 9d and 12d, respectively therethrough. For reasons which will be explained later on, there are restrictions in size and shape of the support plate 20 and therefore a problem arises that the escape holes 20b cannot be made larger. That is, the support plate 20 has escape holes 20b so that the magnetic head 19 can follow the oscillation and rocking of a magnetic recording medium (not shown) when the slidable contacting face of the magnetic head 19 is in slidable contact with a magnetic recording medium to perform recording/reproduction of information. In addition, recently, extensive investigation has been made in order to reduce in size floppy disc drive units using the magnetic head 19 described above and increase the density thereof, and accordingly the appearance and shape of the support plate 20 have been reduced in size in accordance with such activities. The smaller the support plate 20, the more difficult it is for the dimension "h" of the support plate 20 as shown in FIG. 6 to be enlarged, resulting in that the mechanical strength of the support plate 20 decreases causing the problem that deformation tends to occur.
Furthermore, it would be necessary to form holes 21b for inserting therein terminals 9d and 12d in the flexible printed board 21 at positions corresponding to the terminals 9d and 12d, respectively. The size of the holes 9a and 12a formed in the bobbins 9 and 12 are made somewhat larger than the size of the core 2a and 4a so that the cores are not damaged when the cores 2a and 4a are inserted in the holes 9a and 12a, respectively, at the time of assembling. Hence, fluctuations in the distance between the terminals 9d and 12d as well as in their positions tend to occur due to fluctuations in the size of core assembly 1 and the clearances of the holes 9a and 12a of the coil bobbins 9 and 12, respectively. Therefore, it becomes necessary that the holes 21b in the printed board 21 be larger in size than the terminals 9d and 12d, respectively. However, it is sometimes difficult to make the connection portions 21a larger depending on the size of the support plate 20. As a result, it has often been the case that when the printed board 21 is fabricated, the connection portions 21a are cut, thereby decreasing processing yield which in turn causes an increase in the cost of parts.
Because the coil bobbins 9 and 12 have flanges 9b and 12b which are too thin, and therefore their moldability is too poor, to fabricate them using a material having a higher thermal resistance, there results an increase in cost of material and an aggravation of yield, thus considerably aggravating productivity, which are factors for increasing the cost of production of the coil bobbins 9 and 12.
Further, the shield ring 22 is bonded to the support plate 20, which in turn is fixed to the magnetic head 19. In accordance with the recent trend in which the size of floppy disc drives has been reduced, it becomes necessary to make the support plate 20 smaller, which reduces space for mounting the shield ring 22. Therefore, it is difficult to coat a sufficient amount of adhesive, and accordingly the adhesion strength decreases due to aging of the adhesive. In this case, it is sometimes the case that the shield ring 22 will drop off from the magnetic head body 18 as a result of vibration or shock accompanying by the head seeking action or the like of the floppy disc drive.
In the case where the shield ring 22 is made of a magnetic material such as Permalloy, it is necessary to attach it to the support plate 20 by positioning it so that there is a predetermined clearance from the magnetic head body 18. This operation is also cumbersome and takes a long time, thus causing an obstacle to the simplification of production steps.